Improved thermal interface property of carbon nanotube-Cu composite based on supercritical fluid deposition

In this paper, we present a new synthesis method of carbon nanotubes (CNTs)-copper (Cu) composite on a silicon substrate using combination of supercritical fluid deposition (SCFD) and electrochemical plating (ECP) process. Deposition of a Cu layer onto CNTs is carried out under supercritical condition, and the CNTs-Cu composite with high-density Cu is synthesized by additional ECP process. The Cu layer deposited by SCFD functions as a seed layer for ECP, and spaces between neighboring CNTs are filled by Cu. The measured density of the CNTs-Cu composite is 8.2 ± 0.3 g/cm³, and the volume percentage of voids is 3-6%. The evaluated thermal resistance including the thermal interface resistance and bulk resistance of the composite is as low as 28.4 mm² K W^-1 at a contact pressure of 0.2 MPa. A CNT brush formed on the composite surface can reduce the thermal resistance to be 68.4 mm² K W^-1 at a contact pressure of 0.25 MPa. The CNTs-Cu composite shows the ability applicable to many microelectronics applications as a thermal interface material.